Multi-compartment water-soluble detergent capsules made with water-soluble film are known. The water soluble-film is typically polyvinyl alcohol. The preferred capsule manufacturing process involves thermoforming the film. By thermoforming is meant a process in which a first sheet of film is subjected to a moulding process to form recesses in the film. The process involves heating the film to soften it and also the application of vacuum to hold the film in the moulds. The recesses are then filled, typically with a detergent liquid. The capsules are completed by overlaying a second sheet over the filled recesses and sealing it to the first sheet of film around the edges of the recesses to form a flat seal area. Relaxation of the first film typically then causes the applied second sheet to bulge out when the vacuum is released from the first sheet of film in the mould. The capsules are cut apart to leave part of the flat seal area as a peripheral “skirt” around each capsule when it is removed from the mould. Although the seal is flat when in the mould it may deform a little when removed from the mould. Likewise a rectangular profile capsule usually relaxes slightly away from having a perfect rectangular profile after it is released from the mould. Throughout this specification flat seals are ones that are moulded flat and rectangular capsules are ones formed in rectangular moulds, usually with their corners rounded off. Multi-compartment capsules are suited for delivery of main wash laundry compositions to automatic washing machines and even for hand wash applications. Although a multi-compartment configuration is more difficult to manufacture than a single compartment it may be chosen because components of the detergent composition need to be mixed at point of use and/or have reduced stability when stored together. It may also give the capsule aesthetic appeal because the different compartments can be filled with different coloured contents. In general the formulator would like to keep the number of compartments to a minimum in order to avoid complexity and added cost.
Multi-compartment water-soluble detergent capsules comprising from 2 to 5 compartments obtained by thermoforming a water-soluble film are disclosed in EP 1375637 and EP 1394065 (Unilever). Each compartment of the package contains a different part of a cleaning composition and the compartments are connected to each other and separated from one another by at least one flat seal area. One compartment may contain a liquid part of the detergent composition and another compartment a granular part of the composition, such as bleach or builder. A problem with capsules having their compartments separated by a flat seal area that extends across the capsule as described in most of the embodiments disclosed is that they are floppy because they will fold up along the flat seal. This folding has been found to cause handling problems and a floppy capsule is not liked by consumers. FIG. 1 shows plan and side elevations of a foldable two-compartment water-soluble capsule as described in these documents. FIG. 2 shows the one embodiment (FIG. 1d) from EP 1375 637A1 that does not suffer from this undisclosed folding problem. A generally rectangular compartment surrounds a small circular compartment. From paragraph 0079 we are told that the larger compartment contained 50 ml of the liquid formulation and the small compartment 7 g of the semi-solid formulation. According the preceding paragraph 0078 the liquid composition comprised:
IngredientParts by weightLAS, monoethanolamine salt24.0Nonionic 7EO20.3Soap22.4Monopropyleneglycol23.7Moisture, salts, NDOM6.9Minors (enzymes, polymers, perfume)2.7
From paragraph 0077 it is disclosed that the semi solid composition comprised:
IngredientParts by weightNa-LAS39.1Nonionic 7EO33.5C12 soap7.3Monopropyleneglycolto 100
In WO2010 0088112 a two compartment “stacked” capsule is made having a smaller liquid compartment and a larger powder compartment. The two compartments are separated only by a thin layer of polyvinylalcohol film. The disclosure is mainly focused on dishwashing compositions and the exemplary two compartment capsule has the following liquid and granular compositions in its compartments:
% in% inIngredientcompartmentcapsulePercarbonate bleach74.964.369Acrylic acid/maleic acid copolymer7.56.446Polyacrylate or polycarboxylate polymer1311.172Proteases and amylase enzyme mix32.578HEDP granular1.51.289Perfume0.10.086Total in powder compartment10085.94Dipropylene glycol57.295.970Glycerine2.990.312Colour0.90.094Surfactant LF24429.473.071Nonionic surfactant2.630.274Water6.720.700Total in liquid compartment100.0010.42
It was also known, from the product sold as “Tide Pods” or “Ariel Pods”, to assemble two thermoformed “capsules” to form a multi-compartment capsule whereby a first “capsule” having at least two smaller liquid compartments joined together with foldable flat seals is then used to seal a larger compartment. This configuration prevents the seals from folding. However, this approach suffers from the disadvantages of a complex manufacturing process and having a seal area with triple layers of film. To avoid dissolution problems resulting from such triple layer seals it is necessary to use thinner than normal film, which leads to issues with leakage due to pin-holing of the thinner film elsewhere in the capsules during manufacture.
Polyvinylalcohol film cannot completely prevent migration of the contents of one liquid compartment into another. In any capsule where there is a liquid compartment separated from other ingredients only by a single thin layer of polyvinylalcohol film the ability to effectively segregate ingredients that need to be kept apart until use is inevitably compromised. For example in the three compartment capsule, only the contents of the two smaller liquid compartments can be considered to be effectively segregated, so it takes a minimum of three compartments to achieve significant segregation benefits when using this approach. The need to include sensitive ingredients in the smaller compartments then drives complexity as more and more of the smaller compartments are needed to keep these sensitive ingredients segregated from one another.
An alternative to thermoforming of capsules is a vertical form fill seal process (VFFS). US 2001/0033883 (Body) discloses multi-compartment capsules having separate compartments for granular and liquid materials, preferably popcorn kernels and oil, the contents being packed so that they can move within their respective compartments on the application of an external force thereby inhibiting the rupture of the compartments. A two compartment capsule has three layers of film. The extra third layer being used to form an internal partition between the fluid material in one compartment and the granular materials in a second compartment. If applied to a detergent composition this construction suffers from possible contamination of the granular compartment by transfer of liquid through the film. Such preformed packs are also more expensive to produce than thermoformed packs.
A known issue with water-soluble detergent capsules, including those used in automatic laundry washing machines, is that consumers do not read the instructions for their use carefully and therefore may use them incorrectly. They are known to put the capsule into the washing machine dispensing drawer when it should be added directly to the drum and they are also known to use capsules in overloaded water conserving washing machines where the capsule may then not be exposed to much water.
There is a need for an improved multi-compartment water-soluble thermoformed capsule design, particularly one that uses only two layers of water-soluble film and is capable of withstanding the expected abuses by consumers.